Cardiopulmonary resuscitation (CPR) during spaceflight - a guideline for CPR in microgravity from the German Society of Aerospace Medicine (DGLRM) and the European Society of Aerospace Medicine Space Medicine Group (ESAM-SMG).

BACKGROUND: With the "Artemis"-mission mankind will return to the Moon by 2024. Prolonged periods in space will not only present physical and psychological challenges to the astronauts, but also pose risks concerning the medical treatment capabilities of the crew. So far, no guideline exists for the treatment of severe medical emergencies in microgravity. We, as a international group of researchers related to the field of aerospace medicine and critical care, took on the challenge and developed a an evidence-based guideline for the arguably most severe medical emergency - cardiac arrest. METHODS: After the creation of said international group, PICO questions regarding the topic cardiopulmonary resuscitation in microgravity were developed to guide the systematic literature research. Afterwards a precise search strategy was compiled which was then applied to "MEDLINE". Four thousand one hundred sixty-five findings were retrieved and consecutively screened by at least 2 reviewers. This led to 88 original publications that were acquired in full-text version and then critically appraised using the GRADE methodology. Those studies formed to basis for the guideline recommendations that were designed by at least 2 experts on the given field. Afterwards those recommendations were subject to a consensus finding process according to the DELPHI-methodology. RESULTS: We recommend a differentiated approach to CPR in microgravity with a division into basic life support (BLS) and advanced life support (ALS) similar to the Earth-based guidelines. In immediate BLS, the chest compression method of choice is the Evetts-Russomano method (ER), whereas in an ALS scenario, with the patient being restrained on the Crew Medical Restraint System, the handstand method (HS) should be applied. Airway management should only be performed if at least two rescuers are present and the patient has been restrained. A supraglottic airway device should be used for airway management where crew members untrained in tracheal intubation (TI) are involved. DISCUSSION: CPR in microgravity is feasible and should be applied according to the Earth-based guidelines of the AHA/ERC in relation to fundamental statements, like urgent recognition and action, focus on high-quality chest compressions, compression depth and compression-ventilation ratio. However, the special circumstances presented by microgravity and spaceflight must be considered concerning central points such as rescuer position and methods for the performance of chest compressions, airway management and defibrillation.

The effects of prolonged acute hypobaric hypoxia on novel measures of biventricular performance.

BACKGROUND: There are limited data on the effects of prolonged acute hypoxia on individual and global measures of biventricular function. AIMS: The aim of this study was to assess its effects on conventional and novel measures of biventricular function, including the recently defined E'/(A'×S') (EAS) index, obtained using pulsed-wave tissue Doppler Imaging (PWTDI) and associated blood brain natriuretic peptide (BNP) levels. METHODS: In this study, 14 healthy subjects aged 30.5 years were assessed at baseline and at >150 minutes following hypobaric hypoxia (HH) to the equivalent altitude of 4800 m for a total of 180 minutes. The combined EAS index (E'/(A' × S')) was calculated at the mitral and tricuspid annulus using data from the peak systolic (S') early (E') and late (A') diastolic filling. RESULTS: It was seen that HH increased resting heart rate (63.4 ± 8.4 vs. 85.2 ± 10.2/min; P < 0.0001), cardiac output (4.6 ± 0.7 L/min vs. 6.1 ± 1.2 L/min; P < 0.0001), peak pulmonary artery systolic pressure (PASP) (26.3 ± 2.0 mmHg vs. 37.2 ± 6.3 mmHg; P < 0.0001), and reduced SpO2 (98.5 ± 1.1 vs. 72.9 ± 8.1%; P < 0.0001). There was a significant reduction in mitral (0.19 ± 0.06 vs. 0.11 ± 0.03; P < 0.0001) and tricuspid (0.12 ± 0.04 vs. 0.09 ± 0.03; P = 0.03) EAS indices, but no change in left or right ventricular myocardial performance (Tei) indices, global left ventricular (LV) longitudinal systolic strain, BNP levels, or estimated filling pressures (E/E'). Only reducing SpO2 remained as an independent predictor of PASP on multivariate analysis (overall R(2) = 0.77; P < 0.0001). The right and LV EAS indices were significantly correlated (r = 0.45; 95% CI: 0.07-0.7; P = 0.02). CONCLUSION: The conclusion from this study was that acute prolonged HH does not adversely affect resting global biventricular function and there is evidence of linked right and LV responses.

Brain natriuretic peptide and acute hypobaric hypoxia in humans.

In animal models, the secretion of the cardiac hormone, brain natriuretic peptide (BNP), and its closely related peptide, atrial natriuretic peptide (ANP), are stimulated by acute hypoxia. There is extensive human evidence for a rise in ANP under acute hypoxic conditions but very little evidence regarding the BNP response to acute hypoxia in humans. We therefore subjected seven healthy subjects to an acute hypobaric hypoxic stimulus to examine if BNP secretion increases rapidly. Significant hypoxaemia (mean nadir oxygen saturation 62.3%) was induced but no significant rise in BNP occurred. This suggests that either such acute hypoxaemia is well tolerated by the healthy human heart or it is not a stimulus for BNP secretion.

Effects of altitude exposure on brain natriuretic peptide in humans.

Acute mountain sickness (AMS) is common at high altitude (HA) and associated with a relative failure of the natriuresis and diuresis that occurs at HA. The role of Brain Natriuretic Peptide (BNP) in this context has not been thoroughly investigated. We aimed to clarify if BNP rises in response to exercise at HA and if so whether this is related to AMS. 32 healthy subjects had assessments of BNP, aldosterone and AMS scores [as assessed by the AMS-C score of the Environmental Symptom Questionnaire (ESQ) and Lake Louise questionnaire] made following exertion at sea-level (SL), 3,400, 4,300 and 5,150 m. Data were analysed in the 23 subjects who did not consume drugs known to affect acclimatization. BNP (pg/ml, mean ± SEM) was significantly higher at 5,150 m versus the lower altitudes (p < 0.001 for all): 7.1 ± 1; 6.1 ± 0.3; 6.8 ± 0.9 and 17.7 ± 5.1 at sea-level; 3,400, 4,300 and 5,150 m. In those that showed a BNP response at 5,150 m (n = 19) versus those that did not demonstrate a BNP response (n = 4) there was a significant difference in Lake Louise (LL) AMS scores at 5,150 m on day 10 of the expedition (mean LL score 3.3 vs. 0.75, p = 0.034) and day 11 (mean LL score 3.3 vs. 0, p = 0.003). This is the first report to demonstrate a significant rise in BNP at HA. A BNP response at 5,150 m may be associated with a greater likelihood of suffering AMS.